<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    a:link {
        color: red;
    }

    a:visited {
        color: blue;
    }

    a:hover {
        color: #73AD21;
    }

    a:active {
        color: darkviolet;
    }

    input:focus {
        outline: 10px solid #FF0000;
    }

    ul li:first-child{
        color: red;
    }
    ul li:last-child{
        color: blue;
    }
    ul li:nth-child(2){
        color: orange;
    }
</style>
<body>

<div>

    <a href="#">单机啊啊啊啊啊啊啊啊</a>
    <hr>
    <input type="text"/>
    <hr>
    <ul>
        <li>aaaa</li>
        <li>aaaaaa</li>
        <li>aaaaaaaa</li>
        <li>aaaaaaaaaa</li>
    </ul>

</div>
</body>
</html>